The invention relates generally to heat exchange devices for heating and/or cooling of the human body, and more particularly to a patient therapy heat exchange structure for placing against or for being worn on the human body. The heat exchange structure can be in combination with a cooperating portable device, which may be in the form of a wheeled cart, for providing heating and/or cooling liquid to the patient therapy device at a desired temperature, with or without cyclic pressurization.
U.S. Pat. No. 4,691,762 discloses a temperature control system including a heat exchanger vest and/or helmet to be worn on the human body, accompanied by a portable unit which administers cooling to a circulated liquid which passes through the heat exchange garments. The heat exchange garments pursuant to that patent were advantageously formed as Flexitherm (a trademark of Life Support Systems, Inc.), a material, fabricated of two sheets of flexible, liquid-impervious plastic material heat sealed together to form the fluid conducting channels with appropriate manifolding.
The Flexitherm heat exchange material as constituted prior to this invention had a tendency to exhibit flow constriction problems under certain circumstances. For example, in areas where the heat exchange material was subjected to relatively sharp bends, crease lines could form in the manifolds and in the fluid conducting channels themselves due to the stresses of bending the material when pressurized with flowing liquid. These stress lines or crease lines could become deep creases and shut off flow to some flow channels and through some portions of the manifolds. The problem was accentuated further by the imbalance in pressurization shrinkage between the flow channels and the manifolds. The flow channels shrink in lateral dimension when pressurized with liquid, since the flattened channels become xe2x80x9cinflatedxe2x80x9d to a generally cylindrical configuration, drawing the structure inward laterally. Adjacent manifolds, which are generally perpendicular to the orientation of the flow channels, shrink in the perpendicular direction, but essentially do not shrink in the direction of shrinkage of the flow channels. Upon pressurization this imbalance tended to put increased stress on the manifolds, tending to form constrictions which were even more greatly accentuated when the Flexitherm heat exchange structure was formed around curves and bends on the body.
These problems limited the usefulness of the Flexitherm material for additional therapy situations which might require relatively sharp bends and flexing situations.
Co-pending application Serial No. 431,753, which was a division of application Ser. No. 250,778 (U.S. Pat. No. 4,884,304), disclosed a bedding system with liquid heating or cooling, wherein the liquid temperature control was provided by a mixing device which mixed warm liquid with cooled liquid as selected by the user, for maximum comfort. This provided for fast-response adjustment of temperature (and individual control in a dual control system) in the liquid flow channels of the bedding system, to quickly achieve the proper temperature for the particular user.
Such closed-loop mixing of heated and cooled liquids, to quickly achieve changes in temperature in a liquid-conducting flexible heat exchange device, was not generally available prior to the present invention. Conventional systems which have been in use have had only a single liquid tank, with the requirement of changing the temperature of water in the tank in order to achieve a change in temperature in a heat exchange device served by the tank. For example, heating/cooling devices of this general type have been available from Zero Cincinnati, Baxter Medical and Jobst.
It is an object of the present invention to provide an improved flexible heat exchange structure which may be used for thermal therapy on a patient or for other body cooling purposes, and this may be in conjunction with a portable source of heated and/or cooled liquid, and optionally air pressure, connected to the heat exchange structure or garment by fluid lines, for achieving very fast response in temperature adjustment for the patient thermal therapy.
In accordance with one embodiment of the invention, a flexible heat exchange structure, which may be used for heating and/or cooling of the human body, particularly for medical purposes but also for body thermal control in extreme environments, has a plurality of fluid conducting channels for carrying a heat exchange liquid. The channels are formed between a pair of flexible sheets of material, substantially impervious to the heat exchange liquid, with the sheets sealed together along generally parallel lines to form the liquid conducting channels between the lines. At the ends of the series of liquid conducting channels are manifolds for conducting the heat transfer liquid into the series of channels and out of the series of channels.
The pair of flexible sheets are sealed together around the series of liquid conducting channels along peripheral seal lines, spaced away from the ends of the channels in manifold portions so as to define the manifolds for inflow and outflow of liquid. In accordance with the invention the manifold portions of the seal lines have portions formed in a convoluted or undulating pattern. This pattern tends to discourage pinching of the fluid manifolds when the flexible heat exchange structure is subjected to bending or flexure as when worn on the human body. Further, the convoluted or undulating manifold seal lines tend to reduce buckling stress in the manifolds on pressurization of the heat exchange structure, by balancing pressurization shrinkage at the manifold portions of the seal lines with pressurization shrinkage laterally among the liquid conducting channels.
The sheets of flexible material preferably are heat sealed to form the seal lines, with the heat seals in a preferred embodiment being approximately 0.1xe2x80x3 wide. Between the heat seal lines the fluid conducting channels may be approximately 0.15xe2x80x3 wide when in flattened configuration. The convolutions in the manifold seal lines may have a width of about 0.5xe2x80x2, forming a relationship discussed further below.
The convoluted or undulating pattern of seal lines can comprise a pattern of generally curved undulations, the undulations each having a width which is selected to shrink, upon pressurization of the heat exchange structure with fluid, to the same degree that the liquid conducting channels on the other side of the manifold shrink in width. This avoids the differential pressurization shrinkage mentioned above. The undulations may be generally semi-circular in shape, or U-shaped, or they may V-shaped, with the open side of the U or V shape facing toward the series of liquid conducting channels on the other side of the manifold. In a preferred embodiment the apices of the generally curved undulations (xe2x80x9cgenerally curvedxe2x80x9d includes V-shaped undulations), are positioned to be oriented generally toward the center of the open end of every second flow channel on the other side of the manifold, and generally equidistant from the two heat seal ends of the respective flow channels.
In a further preferred embodiment, the flow channels or capillaries of the heat exchange structure, while still being generally linear in an overall sense, are formed by seal lines in zig-zag patterns, the seal lines being regular repeating zig-zag lines generally equally spaced apart to form the liquid conducting channels between them. This zig-zag pattern of the channels tends to discourage pinching of the channels when the flexible heat exchange structure is subjected to bending or flexure, particularly around relatively tight bends or curves, as when worn on the human body.
In a further implementation of the invention a third flexible sheet of material is secured to the two-ply material, connected by sealed connection to one side of the fluid channel structure. This forms an air envelope between one of the pair of flexible sheets and the third sheet. Pressurized air can be received in this air envelope, to pressurize the heat exchange therapy device against the skin, such as on a human limb or torso, so that a combination of thermal therapy and pressure therapy can be applied to an injured area. The pressure also aids in conducting the heating or cooling into the skin, and it can be effective to control blood flow or swelling in the treated area.
In a still further implementation, a fourth sheet of flexible material is secured to the heat exchanger/fluid channel structure, on the opposite side from that of the air envelope. This forms a liquid or gel envelope within which a liquid or gel is contained, preferably permanently. The liquid or gel envelope disperses heating or cooling evenly against the patient""s skin, especially when the air envelope is pressurized. This is important in critical hyperthermia or hypothermia treatment, where relatively extreme temperatures are involved and it is undesirable to have the thermal treatment applied in the discrete lines of the flow channels.
The apparatus of the invention further includes a portable device, which may be in the form of a wheeled cart, for administering the thermal therapy to a patient via the flexible heat exchange structure worn by the patient. Included in the portable device are two reservoirs, a heated liquid reservoir and a cooled liquid reservoir. A return reservoir, also for filling, preferably also is included. A mixing valve is provided to enable selection of precise temperature desired for the patient therapy, by adjusting the mixture of heated liquid and cooled liquid to be delivered to provide the correct temperature. Instantaneous changes may be made, as desired in certain types of patient therapy, by shifting of the mixture. Adjustments may be made anywhere from 100% cooled liquid to 100% heated liquid, by adjustment of the mixing valve.
Liquid which has passed through the patient therapy flexible heat exchange device via a pump reenters the portable apparatus into a return area. This return liquid is heated or cooled proportionally in accordance with the current setting of the mixing valve, as it re-enters the respective reservoirs. This provides for maximum efficiency of the portable device, and is advantageously achieved by providing closed, (substantially) full reservoirs which may have the chiller/heater unit inside the reservoir or in contact with the reservoir. The closed, non-vented reservoirs automatically receive the same return flow rate as the outgoing flow rate. Preferably a return reservoir, vented to atmosphere, first receives the return liquid, and the liquid is pumped from the return reservoir to the cooled and heated reservoirs in accordance with outflow from each reservoir.
Preferably the portable device also includes a source of pressurized air, i.e. a small compressor or pressurized air supply. This provides pressurized air for use in the air envelope discussed above, for administering pressure as well as hot/cold therapy to a patient.
It is therefore among the objects of the invention to provide improved apparatus and methods for administering cooling and/or heating to the human body, including a relatively constriction-free thermal flexible thermal therapy heat exchanger and a portable device for fast-response adjustment of hot/cold therapy. These and other objects, advantages and features of the invention will be apparent from the following description of preferred embodiments, considered along with the accompanying drawings.